Ingo Molnar [off-list ref] writes:

yeah, it's really ugly. But otherwise i've got no real complaint about 
ext3 - with the obligatory qualification that "noatime,nodiratime" in 
/etc/fstab is a must. This speeds up things very visibly - especially 
when lots of files are accessed. It's kind of weird that every Linux 
desktop and server is hurt by a noticeable IO performance slowdown due 
to the constant atime updates, while there's just two real users of it: 
tmpwatch [which can be configured to use ctime so it's not a big issue] 
and some backup tools. (Ok, and mail-notify too i guess.) Out of tens of 
thousands of applications. So for most file workloads we give Windows a 
20%-30% performance edge, for almost nothing. (for RAM-starved kernel 
builds the performance difference between atime and noatime+nodiratime 
setups is more on the order of 40%)

I always thought the right solution would be to just sync atime only
very very lazily. This means if a inode is only dirty because of an
atime update put it on a "only write out when there is nothing to do
or the memory is really needed" list.

-Andi

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